There are so many confounding variables here I don’t know where to begin, so I’ll just post the study, in the hope that it convinces somebody to eat some tofu or cheese instead of some ethically dubious meat:

Children with high IQs are more likely to be vegetarians when they grow up, according to research reported on Friday.

A British study of more them 8,000 men and women aged 30 whose IQs had been measured when they were 10, showed that the higher the IQ, the greater the odds of being a vegetarian.

“People who are more intelligent as children, who will obviously keep that intelligence when they are 30, were more likely to say they are vegetarians at that age than those that were less intelligent,” said Dr Catherine Gale, an epidemiologist at the University of Southampton in England.

She added the findings, which are published online by the British Medical Journal, were consistent with other studies showing people who are more intelligent tend to eat a healthier diet and exercise more.

I would hypothesize that communists, libertarians, feminists and so on are also smarter (except for in places where these belong to the mainstream, so e.g. Swedish feminists or Vietnamese communists might not be über smart), and that the reason is at least partly the same as for vegetarians in Britain.

Also, it would be interesting to see a similar study done in a culture where vegetarianism is part of the mainstream, e.g. among Brahmins.

Perhaps people who choose non-standard ‘-isms’ are more likely to have higher IQs.

It’s worth noting that the IQ differences reported here are remarkably tiny. I wish I could access the raw data – it’s possible that the vegetarian group has a few more high-IQ people and that most of the people in the group are indistinguishable from non-vegetarians, IQ-wise.